Decomposition
and oxidation of methanol on Pt(111) have been examined
between 300 and 650 K in the millibar pressure range using in situ
ambient-pressure X-ray photoelectron spectroscopy (XPS) and temperature-programmed
reaction spectroscopy (TPRS). It was found that even in the presence
of oxygen, the methanol decomposition on platinum proceeds through
two competitive routes: fast dehydrogenation to CO and slow decomposition
via the C–O bond scission. The rate of the second route is
significant in the millibar pressure range, which leads to a blocking
of the platinum surface by carbon and to the prevention of further
methanol conversion. As a result, without oxygen, the activity of
Pt(111) converted to a turnover frequency is ∼0.3 s–1 at 650 K. The activity strongly increases with oxygen content, achieving
20 s–1 in an oxygen-rich mixture. The main products
of methanol oxidation were CO, CO2, H2, and
H2O. The CO selectivity as well as the H2 selectivity
decrease with the increase in oxygen content. It means that the main
reaction route is the methanol dehydrogenation to CO and hydrogen;
however, in the presence of oxygen, CO oxidizes to CO2 and
hydrogen oxidizes to water. At room temperature, the C1s spectra contain
weak features of formate species. This finding points out that the
“non-CO-involved” pathway of methanol oxidation realizes
on platinum as well. However, the TPRS data indicate that at least
under the oxygen-deficient conditions the methanol dehydrogenation
pathway dominates. A detailed reaction mechanism of the decomposition
and oxidation of methanol agreeing with XPS and TPRS data is discussed.
We report the results of the implementation of a quantum key distribution (QKD) network using standard fibre communication lines in Moscow. The developed QKD network is based on the paradigm of trusted repeaters and allows a common secret key to be generated between users via an intermediate trusted node. The main feature of the network is the integration of the setups using two types of encoding, i.e. polarisation encoding and phase encoding. One of the possible applications of the developed QKD network is the continuous key renewal in existing symmetric encryption devices with a key refresh time of up to 14 s.
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